US2015153317 discloses software that can be used to combine data from local, inexpensive dust sensors (particle counters) with Internet-available rich data on pollutants, weather, optional household devices, sensors, and appliances to create a rich picture of the local environment, shape that environment through non-trivial control of said household appliances and ventilation systems to reduce buildup of household dust on surfaces or reduce sensitive individuals' exposure to specific pollutants, and monitor individuals' exposure to pollutants. The software might live in a smartphone, related hardware devices (such as a pollution sensor communicating via bluetooth with the smartphone) or in heating/cooling control system such as a common household thermostat. In particular, advanced control of windows or inexpensive air filters within a common forced air climate system to mitigate air pollution inexpensively are envisioned. The author envisions an electronic home control system that would monitor indoor dust levels (by means of aforementioned inexpensive dust sensor means) and outdoor dust awareness (either by inexpensive outdoor dust sensors, or by obtaining the information over the Internet) to detect indoor pollution (e.g., caused by a dishwasher) or anticipate the pollution (by notification from the appliance that it is about to operate), open the window whenever the sensed or anticipated indoor air pollution exceeds the sensed or modeled outdoor air pollution, and close the window once indoor air quality has been equalized with outdoor air quality.
US20150108119 relates to microwave appliances and methods for operating microwave appliances. The specification describes a microwave appliance with features for indicating a need for an air filter change and a microwave appliance with features that reduce the risk of prolonged air filter use.
Indoor air pollution is a very serious topic in many parts of the world. Air purifiers are applied widely to deal with this challenge.
Part of the indoor pollution is generated indoors, such as some volatile organic compounds (VOCs). Examples are formaldehyde from furniture, and benzene from decoration materials. Particulate air pollution also arises, for example, from cooking and ironing, but also from peeling an orange or lighting and burning candles or cigarettes. In addition, particulate air pollution also enters homes from outdoors.
It is known to provide an air treatment system which combines sensing of the air quality by one or more sensors and also air purification, using one or more filters. The air purification may be controlled in dependence on the sensing results, to maintain desired air quality levels.
In many cases, indoor activities not only cause problems for a householder as a result of the deteriorated air quality, but also there may be a reduction in the operational lifetime of the filters used in an air purifier. For example, frying results in oily particles that can clog activated carbon filters. Similarly, there may be a reduction in the operational lifetime or performance of the sensors used within the system.
The sensors may for example comprise particle sensors for measuring the level of particulate pollution in the air. These may be based on the measurement of light scattered by the particles that pass along with an air flow through a detection volume in the sensor. The optical components can become adversely affected by the deposition of particulate or VOC deposits over time, so that the lifetime of the sensor is reduced.
Air quality sensors do not have perfect selectivity, in that they may respond to analytes other than those which are designed to be detected. This is particularly the case for low cost sensors. However, the use of low cost sensors is important, particularly in a system which has many sensors networked together.